Abstract: Variation of the wavelength of the light emitted from a light source is reduced by a wavelength variation reduction mechanism. Hence, wavelength deviation of the intensity peak of the light emitted from the light source from the diffraction-efficiency peak of a hologram optical element is reduced. Thus, even when a high-brightness light source is used, the light emitted therefrom can be diffracted with the hologram optical element efficiently. Moreover, the heat generated by the light source is efficiently rejected through the surface of a land portion of a flexible printed circuit, is then, via an insulating layer of the flexible printed circuit, efficiently absorbed through the surface of a heat absorbing member, and is then, via a shield conductor, led out of a casing, so as to be thereby expelled.

Abstract: A photodiode may include a first region comprising substantially intrinsic semiconductor material, the region having a first side and a second side opposite to the first side. The photodiode may also include a second region comprising highly-doped p-type semiconductor material formed proximate to the first side of the first region. The photodiode may additionally include a third region comprising highly-doped n-type semiconductor material formed proximate to the second side of the first region. The photodiode may further include a fourth region comprising one of: (i) highly-doped p-type semiconductor formed between the first region and the third region, or (ii) highly-doped n-type semiconductor formed between the first region and the second region.

Abstract: A hologram optical element is formed on a substrate so as to make an optical device. The hologram optical element is formed in an area smaller than an irradiation area of a beam for reproduction such as image light or object light on the substrate. Supposing that the beam for reproduction is made of a center beam having intensity higher than 50% of center intensity and other peripheral beam, the hologram optical element is formed on the substrate in a size for diffracting only the center beam so that a flare or a ghost can be relieved without using additional optical elements such as a shading plate.

Abstract: A display apparatus which has a mirror with a free curved reflective surface of which curvature fluctuates with inflection points, a liquid crystal display (LCD), a back light and a polarizer. Light of an image which was modulated by the LCD is reflected by the free curved reflective surface and passes through the polarizer. Then, the light is directed to an optical pupil. Since the curvature of the free curved reflective surface fluctuates with inflection points, curvature of field and distortion can be corrected properly, and an image of high quality can be formed.

Abstract: The exposure amounts of R, G, and B laser light emitted from a fabrication light source are so adjusted that the diffraction efficiency at R, G, and B wavelengths in an optical element is commensurate with the light intensity at the R, G, and B wavelengths in the light emitted from a reproduction light source. For example, when the light intensity of the light emitted from the reproduction light source is increasingly low at the B, G, and R wavelengths in this order, the exposure amounts of the R, G, B, laser light emitted from the fabrication light source are so adjusted that the diffraction efficiency in the optical element is increasingly high at the B, G, and R wavelengths in this order. In this way, the hue of the light (reproduction light) obtained from the reproduction light source via the optical element can be adjusted to the hue desired with every reproduction light source used, while the most use is made of the light emitted from the reproduction light source actually used.

Abstract: Variation of the wavelength of the light emitted from a light source is reduced by a wavelength variation reduction mechanism. Hence, wavelength deviation of the intensity peak of the light emitted from the light source from the diffraction-efficiency peak of a hologram optical element is reduced. Thus, even when a high-brightness light source is used, the light emitted therefrom can be diffracted with the hologram optical element efficiently. Moreover, the heat generated by the light source is efficiently rejected through the surface of a land portion of a flexible printed circuit, is then, via an insulating layer of the flexible printed circuit, efficiently absorbed through the surface of a heat absorbing member, and is then, via a shield conductor, led out of a casing, so as to be thereby expelled.

Abstract: A hologram optical element is formed on a substrate so as to make an optical device. The hologram optical element is formed in an area smaller than an irradiation area of a beam for reproduction such as image light or object light on the substrate. Supposing that the beam for reproduction is made of a center beam having intensity higher than 50% of center intensity and other peripheral beam, the hologram optical element is formed on the substrate in a size for diffracting only the center beam so that a flare or a ghost can be relieved without using additional optical elements such as a shading plate.

Abstract: A display apparatus which has a mirror with a free curved reflective surface of which curvature fluctuates with inflection points, a liquid crystal display (LCD), a back light and a polarizer. Light of an image which was modulated by the LCD is reflected by the free curved reflective surface and passes through the polarizer. Then, the light is directed to an optical pupil. Since the curvature of the free curved reflective surface fluctuates with inflection points, curvature of field and distortion can be corrected properly, and an image of high quality can be formed.

Abstract: A display apparatus which has a mirror with a free curved reflective surface of which curvature fluctuates with inflection points, a liquid crystal display (LCD), a back light and a polarizer. Light of an image which was modulated by the LCD is reflected by the free curved reflective surface and passes through the polarizer. Then, the light is directed to an optical pupil. Since the curvature of the free curved reflective surface fluctuates with inflection points, curvature of field and distortion can be corrected properly, and an image of high quality can be formed.

Abstract: When an optical device is produced by bonding on a transparent base member an optical element formed as a hologram, the optical element and the transparent base member are both formed of an acrylic material. In particular when, as an optical device, an eyepiece optical system is produced by holding an optical element between two transparent base members, the optical element, the transparent base members, and the adhesive with which the transparent base members are joined together are all formed of an acrylic material. In this way, by building an eyepiece optical system with a similar kind of material, namely an acrylic material, it is possible to obtain increased adhesion among the materials of the individual components of the eyepiece optical system without performing special processing. Moreover, the transparent base members formed of an acrylic material more securely absorb shock and external pressure than those formed of glass.

Abstract: The exposure amounts of R, G, and B laser light emitted from a fabrication light source are so adjusted that the diffraction efficiency at R, G, and B wavelengths in an optical element is commensurate with the light intensity at the R, G, and B wavelengths in the light emitted from a reproduction light source. For example, when the light intensity of the light emitted from the reproduction light source is increasingly low at the B, G, and R wavelengths in this order, the exposure amounts of the R, G, B, laser light emitted from the fabrication light source are so adjusted that the diffraction efficiency in the optical element is increasingly high at the B, G, and R wavelengths in this order. In this way, the hue of the light (reproduction light) obtained from the reproduction light source via the optical element can be adjusted to the hue desired with every reproduction light source used, while the most use is made of the light emitted from the reproduction light source actually used.

Abstract: A display device has a plurality of light emitting elements for emitting lights, a display element for modulating the light emitting from the plurality of light emitting elements so as to convert it to an image light showing an optical image, a reflection type hologram element, having a positive optical power with respect to the lights from the plural light emitting elements, for diffracting and reflecting the lights from the plural light emitting elements to approximately one direction so as to guide the diffracted and reflected lights to the display element; and an enlarging optical system for forming an enlarged image of the optical image converted by the lights from the image display element. The plural light emitting elements are positioned in a plane approximately vertical to an optical path of the lights diffracted and reflected by the hologram element.

Abstract: A head-mounted image display apparatus is provided with: an image display element; a projection optical system that projects an image displayed by the image display element, so as to be enlarged; a reflective screen onto which the image is projected by the projection optical system; and a combiner disposed between the projection optical system and the screen. The combiner transmits the image light from the projection optical system and directs it to the screen, and reflects the image light reflected at the screen and directs it to the user's pupil.

Abstract: An image display apparatus has an observation room for housing an observer, and the side faces, floor face, and ceiling face of the observation room are used as screens, onto which images displayed on a smaller number of image display devices than the number of screens are projected. At least one image display device displays, on a time-division or screen-division basis, images to be projected onto two or more screens so that images are projected onto all of the screens.

Abstract: An information display device provided with a prism having at least two reflecting surfaces arranged in facing each other and a hologram surface formed of a reflection-type hologram. And at least one of the two reflecting surfaces is a light-beam-selective surface that selectively transmits or reflects light in accordance with its incident angle. An image light emitted from an image display means enters the prism, and is reflected between the reflecting surfaces, and then is diffractively reflected on the hologram surface, and, after being transmitted through the light-beam-selective surface, is directed to an observer's pupil.

Abstract: A viewing optical system of an optical apparatus has an objective system for forming an image of an object and an eyepiece system for enlarging and directing the image to the pupil. The viewing optical system also has a hologram combiner comprising holograms of the volume type, phase type, and reflective type and having optical power for constructing a surface which is optically equivalent to the image surface at a different position than the image when viewed from the pupil. The system also includes an information display means for displaying information at the position of the equivalent surface, wherein the hologram combiner transmits light from the image and reflects light from the information display means so as to allow viewing of an image together with the information display overlaid onto the image.

Abstract: A simple, compact optical system is provided that includes a transmissive optical element and a HOE but that nevertheless does not require an extra optical element for the correction of chromatic aberration. The HOE is designed to have diffractive efficiency for each of R, G, and B light beams and have different focal lengths for those light beams so as to correct the longitudinal chromatic aberration produced by a rectangular parallelepiped prism. This eliminates the need for an extra means for correcting the chromatic aberration produced by the prism. The HOE may be designed to exhibit different angles of diffraction for the R, G, and B light beams so as to correct the chromatic aberration produced perpendicularly to the optical axis by a wedge-shaped prism.

Abstract: An information display device provided with a prism having at least two reflecting surfaces arranged in facing each other and a hologram surface formed of a reflection-type hologram. And at least one of the two reflecting surfaces is a light-beam-selective surface that selectively transmits or reflects light in accordance with its incident angle. An image light emitted from an image display means enters the prism, and is reflected between the reflecting surfaces, and then is diffractively reflected on the hologram surface, and, after being transmitted through the light-beam-selective surface, is directed to an observer's pupil.

Abstract: An image display apparatus is provided for providing a virtual image to an observer. The image display apparatus includes an image display unit, an eyepiece optical system, and a container. The image display unit is for providing modulated light corresponding to the virtual image. The eyepiece optical system is for directing the modulated light from the image display unit to one or both of the observer's eyes. The container is for supporting the image display unit on an edge portion of the eyepiece optical assembly.

Abstract: A simple, compact optical system is provided that includes a transmissive optical element and a HOE but that nevertheless does not require an extra optical element for the correction of chromatic aberration. The HOE is designed to have diffractive efficiency for each of R, G, and B light beams and have different focal lengths for those light beams so as to correct the longitudinal chromatic aberration produced by a rectangular parallelepiped prism. This eliminates the need for an extra means for correcting the chromatic aberration produced by the prism. The HOE may be designed to exhibit different angles of diffraction for the R, G, and B light beams so as to correct the chromatic aberration produced perpendicularly to the optical axis by a wedge-shaped prism.